In order to utilize the full potential of solar cells fabricated on n-type silicon, it is necessary to achieve an excellent passivation on B-doped emitters. Experimental studies on test structures and theoretical considerations have shown that a negatively charged dielectric layer would be ideally suited for this purpose. Thus, in this work the negative-charge dielectric Al2O3 was applied as surface passivation layer on high-efficiency n-type silicon solar cells. With this front surface passivation layer, a confirmed conversion efficiency of 23.2% was achieved. For the open-circuit voltage Voc of 703.6mV, the upper limit for the emitter saturation current density J0e, including the metalized area, has been evaluated to be 29fA∕cm2. This clearly shows that an excellent passivation of highly doped p-type c-Si can be obtained at the device level by applying Al2O3.

This paper presents the first conversion efficiency above 20% for a multicrystalline silicon solar cell. The application of wet oxidation for rear surface passivation significantly reduces the process temperature and therefore prevents the degradation of minority‐carrier lifetime. The excellent optical properties of the dielectrically passivated rear surface in combination with a plasma textured front surface result in a superior light trapping and allow the use of substrates below 100 μm thickness. A simplified process scheme with laser‐fired rear contacts leads to conversion efficiencies of 20·3% for multicrystalline and 21·2% for monocrystalline silicon solar cells on small device areas (1 cm2). Copyright © 2004 John Wiley & Sons, Ltd.

A technique for field effect surface passivation for silicon solar cells Appl. Phys. Lett.

Thermal oxides are commonly used for the surface passivation of high-efficiency silicon solar cells from mono-and multicrystalline silicon and have led to the highest conversion efficiencies reported so far. In order to improve the cost-effectiveness of the oxidation process, a wet oxidation in steam ambience is applied and experimentally compared to a standard dry oxidation. The processes yield identical physical properties of the oxide. The front contact is created using a screen-printing process of a hotmelt silver paste in combination with light-induced silver plating. The contact formation on the front requires a short high-temperature firing process, therefore the thermal stability of the rear surface passivation is very important. The surface recombination velocity of the fired oxide is experimentally determined to be below S £ 38 cm/s after annealing with a thin layer of evaporated aluminium on top. Monocrystalline solar cells are produced and 19Á3% efficiency is obtained as best value on 4 cm 2 cell area. Simulations show the potential of the developed process to approach 20% efficiency.

Fraunhofer ISE's concept for an advanced metallization of silicon solar cells is based on a two-step process: the deposition of a seed layer to form a mechanical and electrical contact and the subsequent thickening of this seed layer by a plating step, preferably by light-induced plating (LIP). The concept of a multi-layer metallization is used for most of the relevant high-efficiency cell types in industry. The main advantage of this concept is that each layer can be optimized individually, i.e. the seed layer to achieve an optimal electrical and mechanical contact and the plated layer in terms of high lateral conductivity and good solderability. Solar cells results with seed layers fabricated by aerosol printing, chemical Ni plating on cells with a laser-structured dielectric layer and laser-enhanced Ni plating are presented